This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Fayadat, L. Articles by Franc, J. L. Search for Related Content PubMed PubMed Citation Articles by Fayadat, L. Articles by Franc, J. L.

Human Thyroperoxidase Is Largely Retained and Rapidly Degraded in the Endoplasmic Reticulum. Its N-Glycans Are Required for Folding and Intracellular Trafficking

Institut National de la Santé et de la Recherche Médicale (Unité 38), Faculté de Médecine, Université de la Méditerranée, 13385 Marseille, Cedex 5, France

Address all correspondence and requests for reprints to: Jean-Louis Franc, INSERM U38, Faculté de Médecine, 27 Bd Jean Moulin, 13385 Marseille, Cedex 5, France. E-mail: Jean-Louis.Franc{at}medecine.univ-mrs.fr

Human thyroperoxidase (hTPO), a type I transmembrane heme containing glycoprotein, catalyzes iodide organification and thyroid hormone synthesis and plays a major role in thyroid autoimmunity. Whereas hormonosynthesis occurs at the apical membrane of thyroid cells, TPO localizes mainly in the perinuclear membrane and the endoplasmic reticulum. To establish the intracellular trafficking and the structural characteristics of hTPO in the various cell compartments, hTPO was stably expressed in the Chinese hamster ovary cell line, and its folding was studied with two monoclonal antibodies (mAbs): mAb 47, recognizing a linear epitope; and mAb 15, recognizing a conformational epitope present in the mature protein. The results show that only 15–20% of hTPO molecules were able to acquire a conformation suitable for the recognition by mAb 15. On the other hand, only a part (15%) of the latter were able to reach the plasma membrane. The hTPO, unable to fold correctly, was more rapidly degraded than that recognized by mAb 15 (half-time, 2 h vs. 7 h). Study of the carbohydrate content of hTPO showed that N-glycans with complex-type structure were found only on hTPO at the cell surface, whereas intracellular hTPO bore high-mannose-type structures. Taken together, these data demonstrate that the intracellular pool of enzyme is formed of newly synthesized molecules and is not caused by recycling of mature hTPO from the cell surface. Complete inhibition of hTPO N-glycosylation with tunicamycin led to a 95% decrease in hTPO at the plasma membrane and, thus, to a decrease in enzymatic activity at the cell surface, emphasizing the role of N-glycans in the intracellular trafficking of hTPO. However, inhibition of formation of complex-type structures with deoxymannojirimycin and of O-glycans with phenyl--GalNAc did not influence the intracellular trafficking and enzymatic activity of hTPO.

This article has been cited by other articles:

				A. Giraud, P.-J. Lejeune, J. Barbaria, and B. Mallet A Plasminogen-Like Protease in Thyroid Rough Microsomes Degrades Thyroperoxidase and Thyroglobulin Endocrinology, June 1, 2007; 148(6): 2886 - 2893. [Abstract] [Full Text] [PDF]

				J Di Cristofaro, M Silvy, A Lanteaume, M Marcy, P Carayon, and C De Micco Expression of tpo mRNA in thyroid tumors: quantitiative PCR analysis and correlation with alterations of ret, Braf , ras and pax8 genes. Endocr. Relat. Cancer, June 1, 2006; 13(2): 485 - 495. [Abstract] [Full Text] [PDF]

				R. Ameziane-El-Hassani, S. Morand, J.-L. Boucher, Y.-M. Frapart, D. Apostolou, D. Agnandji, S. Gnidehou, R. Ohayon, M.-S. Noel-Hudson, J. Francon, et al. Dual Oxidase-2 Has an Intrinsic Ca2+-dependent H2O2-generating Activity J. Biol. Chem., August 26, 2005; 280(34): 30046 - 30054. [Abstract] [Full Text] [PDF]

				R. Kuliawat, J. Ramos-Castaneda, Y. Liu, and P. Arvan Intracellular Trafficking of Thyroid Peroxidase to the Cell Surface J. Biol. Chem., July 29, 2005; 280(30): 27713 - 27718. [Abstract] [Full Text] [PDF]

				E. M. Pietila, J. T. Tuusa, P. M. Apaja, J. T. Aatsinki, A. E. Hakalahti, H. J. Rajaniemi, and U. E. Petaja-Repo Inefficient Maturation of the Rat Luteinizing Hormone Receptor: A PUTATIVE WAY TO REGULATE RECEPTOR NUMBERS AT THE CELL SURFACE J. Biol. Chem., July 15, 2005; 280(28): 26622 - 26629. [Abstract] [Full Text] [PDF]

				V. Le Fourn, M. Ferrand, and J.-L. Franc Endoproteolytic Cleavage of Human Thyroperoxidase: ROLE OF THE PROPEPTIDE IN THE PROTEIN FOLDING PROCESS J. Biol. Chem., February 11, 2005; 280(6): 4568 - 4577. [Abstract] [Full Text] [PDF]

				C. Rodrigues, P. Jorge, J. P. Soares, I. Santos, R. Salomao, M. Madeira, R. V. Osorio, and R. Santos Mutation screening of the thyroid peroxidase gene in a cohort of 55 Portuguese patients with congenital hypothyroidism Eur. J. Endocrinol., February 1, 2005; 152(2): 193 - 198. [Abstract] [Full Text] [PDF]

				S. Morand, D. Agnandji, M.-S. Noel-Hudson, V. Nicolas, S. Buisson, L. Macon-Lemaitre, S. Gnidehou, J. Kaniewski, R. Ohayon, A. Virion, et al. Targeting of the Dual Oxidase 2 N-terminal Region to the Plasma Membrane J. Biol. Chem., July 16, 2004; 279(29): 30244 - 30251. [Abstract] [Full Text] [PDF]

				M. Ferrand, V. Le Fourn, and J.-L. Franc Increasing Diversity of Human Thyroperoxidase Generated by Alternative Splicing. CHARACTERIZATION BY MOLECULAR CLONING OF NEW TRANSCRIPTS WITH SINGLE- AND MULTISPLICED mRNAs J. Biol. Chem., January 31, 2003; 278(6): 3793 - 3800. [Abstract] [Full Text] [PDF]

				A.-C. Gerard, M.-C. Many, C. Daumerie, S. Costagliola, F. Miot, J. J. M. DeVijlder, I. M. Colin, and J.-F. Denef Structural Changes in the Angiofollicular Units between Active and Hypofunctioning Follicles Align with Differences in the Epithelial Expression of Newly Discovered Proteins Involved in Iodine Transport and Organification J. Clin. Endocrinol. Metab., March 1, 2002; 87(3): 1291 - 1299. [Abstract] [Full Text] [PDF]

				N. Samih, S. Hovsepian, A. Aouani, D. Lombardo, and G. Fayet Glut-1 Translocation in FRTL-5 Thyroid Cells: Role of Phosphatidylinositol 3-Kinase and N-Glycosylation Endocrinology, November 1, 2000; 141(11): 4146 - 4155. [Abstract] [Full Text] [PDF]

				A. L. Stevens, S. Breton, C. E. Gustafson, R. Bouley, R. D. Nelson, D. E. Kohan, and D. Brown Aquaporin 2 is a vasopressin-independent, constitutive apical membrane protein in rat vas deferens Am J Physiol Cell Physiol, April 1, 2000; 278(4): C791 - C802. [Abstract] [Full Text] [PDF]

				L. Fayadat, S. Siffroi-Fernandez, J. Lanet, and J.-L. Franc Calnexin and Calreticulin Binding to Human Thyroperoxidase Is Required for Its First Folding Step(s) But Is Not Sufficient to Promote Efficient Cell Surface Expression Endocrinology, March 1, 2000; 141(3): 959 - 966. [Abstract] [Full Text] [PDF]

				L. Fayadat, P. Niccoli-Sire, J. Lanet, and J.-L. Franc Role of Heme in Intracellular Trafficking of Thyroperoxidase and Involvement of H2O2 Generated at the Apical Surface of Thyroid Cells in Autocatalytic Covalent Heme Binding J. Biol. Chem., April 9, 1999; 274(15): 10533 - 10538. [Abstract] [Full Text] [PDF]

				X. Zhang and P. Arvan Cell Type-dependent Differences in Thyroid Peroxidase Cell Surface Expression J. Biol. Chem., October 6, 2000; 275(41): 31946 - 31953. [Abstract] [Full Text] [PDF]

				L. Fayadat, S. Siffroi-Fernandez, J. Lanet, and J.-L. Franc Degradation of Human Thyroperoxidase in the Endoplasmic Reticulum Involves Two Different Pathways Depending on the Folding State of the Protein J. Biol. Chem., May 19, 2000; 275(21): 15948 - 15954. [Abstract] [Full Text] [PDF]